After several decades of failed and stalled attempts, an adaptation of Emile Zola's gothic novel Thérèse Raquin has finally made it to the screen, with a generic new title that in no way reflects its uproariously weird tone. In Secret's main selling point is its cast, the previously attached Jessica Biel and Gerard Butler having now been replaced by the altogether more compelling duo of Elizabeth Olsen and Oscar Isaac, but strong performances can't elevate it beyond the level of enjoyably ridiculous.

Olsen plays the beautiful, quietly resentful anti-heroine Thérèse, who's adopted as a child by a stern, puritanical aunt (Jessica Lange on scenery-chewing form) and forced into a suffocating, loveless marriage to her sickly cousin Camille (Tom Felton). So overwhelming is her sexual repression that when Isaac's free-spirited artist Laurent shows up at the family's gloomy new home in Paris, all lusty eyes and rugged magnetism, she's literally swooning.

It takes only a few more heavy-lidded glances before the bodice-ripping action begins in earnest, a distinct edge of unintentional comedy dampening the erotic spark between Isaac and Olsen. The level it lands on is somewhere in the ballpark of Carry On Mills & Boon - case in point, a "while you're down there" moment in which Laurent hides under Thérèse's voluminous skirts from Lange's high-strung Madam Raquin.

Tom Felton and Jessica Lange in In Secret

But the triangular dynamic is compelling, Felton's wheezy, earnest Camille flitting nervously at the edge of the pair's all-consuming passion like a doomed butterfly."I was buried alive, and you dug me up too late," Thérèse breathes mid-romp, in a line that foreshadows the impending turn into gothic horror as she and Laurent go to dark lengths to secure a public future together. Given the stark contrast between the hot-blooded Laurent and faintly reptilian Camille, it's easy to understand her desperation.

Zola's novel develops into a gripping, macabre melodrama with shades of Edgar Allen Poe, but first-time director Charlie Stratton badly fumbles the tonal shift. None of these characters command any emotional investment, and so their messy moral decline has no impact - Stratton's screenplay tries far too late to give Thérèse an inner life, while Isaac's Laurent veers from romantic hero to craven sociopath and back at the whims of each scene. Lange's is the one turn that strikes the right note of dark hysteria, but it's a note she hits again and again until the impact is dulled.

The only way to enjoy In Secret is as pure farce, and the supporting cast of colourful caricatures makes it easy enough: John Kavanagh and Matt Lucas are straight out of a Sweeney Todd spinoff as the local police inspector and his son, alongside a chirrupy Shirley Henderson as the latter's wife. Ditto the sloppy anachronistic dialog, which sees 19th century folks spouting lines like, "I won't tell if you won't!"

Even the unintentional fun dries up by the time the glum and grim third act rolls around, Olsen and Isaac utterly adrift as their characters descend into a histrionic, ill-motivated living hell. Despite compelling performers and source material, In Secret is a ham-fisted misfire.